CN114449877A - Core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material and preparation method thereof - Google Patents
Core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material and a preparation method thereof. The composite wave-absorbing material has the frequency of 8.9GHz under the thickness of 3.5mm, the optimal effective wave-absorbing bandwidth (RL) value can reach-71.9 dB, the effective wave-absorbing bandwidth of RL < -10 reaches 16GHz, the S, C, X and Ku frequency bands are covered, and the material has good stability due to the formation of a carbon-coated nickel-cobalt core-shell structure. The wave-absorbing material prepared by the method is environment-friendly, good in stability, wide in wave-absorbing bandwidth, high in reflection loss, simple in process and suitable for mass production.
Description
Technical Field
The invention belongs to the technical field of electromagnetic wave-absorbing materials, and particularly relates to a core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material and a preparation method thereof.
Background
In recent years, with the rapid development of microelectronics, 5G mobile technology, and precision equipment for civil and military use, electromagnetic pollution may harm human health and even cause information leakage. Currently, great efforts are made to obtain an ideal electromagnetic wave absorbing material having high, thin, wide, and light weight. However, it is difficult for an absorbing material to satisfy both a wide Effective Absorbing Bandwidth (EAB) and a satisfactory Reflection Loss (RL).
Among the absorption materials studied, carbon-based materials, which are mainly electrically lossy, are widely used due to their advantages of low density, good chemical stability, high strength, etc., but their poor magnetic properties result in narrow EABs. The CoNi alloy, which is mainly based on magnetic loss, is considered as an important electromagnetic wave absorbing material due to its high saturation magnetization, tunable morphology, and resolvable magnetic permeability in a high frequency range. However, the skin effect, impedance mismatch, high density, susceptibility to oxidation and agglomeration limit their electromagnetic wave absorption properties, and thus the RL and EAB effects are not ideal. Therefore, combining the electric loss and the magnetic loss, achieving impedance matching by utilizing the synergistic effect, and regulating and controlling the micro-morphology to enhance the dielectric loss is an effective method for improving RL.
The invention discloses a preparation method of a nitrogen-doped porous carbon-coated hollow cobalt-nickel alloy composite wave-absorbing material (application publication number CN 112743098A). the invention synthesizes Ni/Co alloy by using hydrazine hydrate, dopamine is polymerized in situ, and porous structure material is obtained by high-temperature calcination, the strongest reflection loss of the prepared wave-absorbing material is about-47.1 dB, and the biggest EAB is about 4.52 GHz. The invention discloses a preparation method of a cobalt-nickel alloy @ nitrogen-doped porous carbon composite microwave absorbing material (application publication No. CN 112266766A). The preparation method of the cobalt-nickel alloy @ nitrogen-doped porous carbon composite microwave absorbing material is characterized in that a layer of COFs is grown on the surface of an alloy in a precipitation polymerization mode, and the obtained CoNi @ COFs composite crystal is pyrolyzed to obtain the hollow cobalt-nickel alloy @ nitrogen-doped porous carbon composite microwave absorbing material with a core-shell structure. The maximum Reflection Loss (RL) of the invention reaches-55.4 dB, EAB exceeds 5.12GHz, and hydrazine hydrate which is easy to prepare poison is used in the same synthesis process.
Disclosure of Invention
The invention provides a preparation method of a core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material, aiming at the problems of complex synthesis steps, poor stability, unfriendly environment, narrow effective wave-absorbing band width, poor wave-absorbing strength and the like of the existing wave-absorbing material.
The technical scheme of the invention is as follows: a preparation method of a core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material comprises the following steps:
step 1: preparation of Ni/Co-MOF precursor:
dissolving sodium salt and nicotinic acid in deionized water and stirring to obtain solution A; putting nickel salt, cobalt salt and polyvinylpyrrolidone into deionized water, and stirring to obtain a solution B; slowly adding the solution B into the solution A and stirring, then transferring the mixed solution into a high-pressure kettle, and reacting for 4-8 hours at the temperature of 100-150 ℃ to obtain a Ni/Co-MOF precursor;
step 2: preparing a Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material:
and pyrolyzing the Ni/Co-MOF precursor for 0.5-2.5 hours at the temperature of 550-700 ℃ in an argon environment at the heating rate of 2-8 ℃/min, and then cooling to obtain the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material Ni/Co @ C with the core-shell structure.
The mass ratio of the sodium salt to the nicotinic acid to the nickel salt to the cobalt salt is as follows: 1:1:2:1 to 4:5:6: 4.
The sodium salt is sodium acetate, and the nickel salt is nickel nitrate.
The cobalt salt is cobalt nitrate.
Preferably, the reaction conditions in step 1 are 120 ℃ for 6 h.
In the step 2, preferably, the heating rate is 2 ℃/min, the heat preservation time is 2h, and the calcining temperature is 600 ℃.
The core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material is applied to a microwave absorbent.
Mixing the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material (Ni/Co @ C) with the core-shell structure with paraffin to obtain the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material microwave absorbent.
The mass ratio of the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material to paraffin is 2: 1-4.
The invention has the beneficial effects that: the invention relates to a preparation method of a wave-absorbing material with simple process, environmental friendliness, strong reflection loss and ultra-wide wave-absorbing bandwidth. The method comprises the following specific steps:
1. the organic ligand nicotinic acid used by the precursor Ni/Co-MOF is non-toxic, the solvent used for synthesis is water, no waste liquid or waste residue is generated, and the method is completely environment-friendly.
2. The invention synthesizes Ni/Co-MOF in advance, obtains the carbon-based composite material with uniformly distributed alloy through pyrolysis, overcomes the defect of high density of pure alloy, and reduces the weight of the wave-absorbing material.
3. The precursor Ni/Co-MOF is calcined to obtain the wave-absorbing material taking carbon as a shell and Ni/Co as a core. Carbon provides electric loss, Ni/Co alloy provides magnetic loss, and electromagnetic loss jointly optimizes impedance matching and improves wave-absorbing performance. And the Ni/Co alloy is tightly wrapped by the carbon layer, so that the oxidation of the alloy is prevented, and the aim of good stability is fulfilled. The nanometer microscopic core-shell structure realizes multiple reflection of electromagnetic waves and increases dielectric loss.
4. The core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material provided by the invention simultaneously meets the requirements of stronger wave-absorbing capacity (RL) and wider effective wave-absorbing bandwidth (EAB), the optimal RL value can reach-71.9 dB when the frequency is 8.9GHz, the effective wave-absorbing bandwidth of RL < -10 reaches 16GHz, S, C, X and Ku frequency bands are covered, and the prepared wave-absorbing material can be applied to different fields in the frequency band of 2-18GHz by adjusting the thickness.
5. The invention has simple process, environment protection, corrosion resistance of materials, low production cost and suitability for mass production.
Drawings
FIG. 1 is an X-ray diffraction (XRD) pattern of Ni/Co @ C-600 of the present invention;
FIG. 2 is an SEM image of a precursor Ni/Co-MOF of the present invention;
FIG. 3 is an SEM image of Ni/Co @ C-600 of the present invention;
FIG. 4 is a TEM image of Ni/Co @ C-600 of the present invention;
FIG. 5 is a wave-absorbing performance diagram of the Ni/Co @ C-600 composite material.
Detailed Description
Example 1
(1) Preparation of Co/Ni-MOF precursors
1.21gCH3COONa·3H2O and 1.22g nicotinic acid were dissolved in 100ml deionized water and stirred for 30 minutes to obtain solution A. Simultaneously 2.1gNi (NO)3)2·6H2O、 1.2gCo(NO3)2·6H2O and 1.1g polyvinylpyrrolidone (PVP) were dissolved in 100ml of deionized water and stirred for 30 minutes to obtain solution B. The solution B was slowly added to the solution a and stirred for 30 minutes. The uniformly stirred mixed solution was then transferred to a 250 ml teflon stainless steel autoclave and reacted at 120 ℃ for 6 hours. Naturally cooling to room temperature to obtain grey blue precipitate, washing with deionized water for 3 times, and vacuum drying at 60 ℃ for 24 hours to obtain the CoNi-MOF precursor.
(2) Preparation of Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material
And putting the Ni/Co-MOF precursor into a crucible, pyrolyzing for 2 hours at the temperature of 550 ℃ in an argon environment at the heating rate of 2 ℃/min, and naturally cooling to obtain the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material (Ni/Co @ C-550).
(3) Ni/Co @ C-550 wave absorbing performance test
And mixing the composite material with paraffin to obtain the Ni/Co alloy @ nitrogen-doped carbon-based microwave absorbing composite material absorbent. The mass ratio of the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material to paraffin is 2: 3.
the electromagnetic parameters are measured by a vector network analyzer, and according to the transmission line theory, the reflection loss of the material to the electromagnetic wave is calculated by the following equation through the complex dielectric constant and the complex permeability under the given frequency and the thickness of the wave-absorbing material.
When the frequency of the wave-absorbing material is 7.1GHz and the thickness of the wave-absorbing material is 5.5mm, the optimal RL value reaches-8.8 dB.
Example 2
(1) Preparation of Co/Ni-MOF precursors
CH3COONa·3H22.42g of O, 2.44g of nicotinic acid and Ni (NO)3)2·6H2O is 3.15g, Co (NO)3)2·6H2Og was 2.4, otherwise as in example 1.
(2) Preparation of core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material
And putting the Ni/Co-MOF precursor into a crucible, pyrolyzing for 2 hours at the temperature of 600 ℃ in an argon environment at the heating rate of 2 ℃/min, and naturally cooling to obtain the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material (Ni/Co @ C-600) with the core-shell structure.
(3) Test of wave absorbing property of Ni/Co @ C-600
The used wave-absorbing material is the composite material prepared in the embodiment 2, and other similar to the embodiment 1, the wave-absorbing material is determined that when the frequency is 8.9GHz and the thickness is 3.5mm, the optimal RL value can reach-71.9 dB, the effective wave-absorbing bandwidth of RL < -10 is up to 16GHz, and the frequency bands of S, C, X and Ku are covered.
Example 3
(1) Preparation of CoNi-MOF precursors
CH3COONa·3H2O3.63 g, nicotinic acid 3.66g, Ni (NO)3)2·6H2O4.2 g, Co (NO)3)2·6H2Og was 3.6, otherwise as in example 1.
(2) Preparation of Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material
And putting the Ni/Co-MOF precursor into a crucible, pyrolyzing for 2 hours at the temperature of 650 ℃ in an argon environment at the heating rate of 2 ℃/min, and naturally cooling to obtain the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material (Ni/Co @ C-650).
(3) Ni/Co @ C-650 wave-absorbing performance test
The wave-absorbing material used was the composite material prepared in example 3, and other examples were the same as example 1, and it was determined that the optimal RL value of the wave-absorbing material could reach-66.3 dB when the frequency was 16.4GHz and the thickness was 2 mm.
Example 4
(1) Preparation of CoNi-MOF precursors
CH3COONa·3H24.84g of O, 6.1g of nicotinic acid and Ni (NO)3)2·6H2O6.3 g, Co (NO)3)2·6H2Og was 4.8, otherwise as in example 1.
(2) Preparation of Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material
And putting the Ni/Co-MOF precursor into a crucible, pyrolyzing for 2 hours at 700 ℃ in an argon environment at the heating rate of 2 ℃/min, and naturally cooling to obtain the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material (Ni/Co @ C-700).
(3) Ni/Co @ C-700 wave-absorbing performance test
The wave-absorbing material used was the composite material prepared in example 4, and other examples were the same as example 1, and it was determined that the optimal RL value of the wave-absorbing material could reach-9 dB at a frequency of 15.1GHz and a thickness of 1.5 mm.
Analysis of drawings
Fig. 1 is an X-ray diffraction pattern of CoNi @ C-600 showing three peaks at 44.5 °, 51.8 ° and 76.3 ° in XRD pattern, corresponding to (111), (200), (220) planes of cubic fcc-Ni (JCPDS No. 04-0850) and fcc-Co (JCPDS No.15-0806), and showing a weak broad peak at 2 θ ═ 24.5 ° due to the typical carbon (002) plane. There is no unwanted peak-out in the figureNow, Ni is described under the protection of an inert atmosphere2+/Co2+The ions are fully reduced by carbon to the alloy Ni/Co.
As can be seen from FIG. 2, the surface of the precursor Ni/Co-MOF is smooth, and from the SEM image of FIG. 3, the surface of Ni/Co @ C-600 becomes rough after calcination and carbonization, and the surface is covered by nanospheres. From the TEM image of FIG. 4, it can be seen that Ni/Co @ C-600 has a core-shell structure. FIG. 5 is a reflection loss plot of Ni/Co @ C-600 showing that at 3.5mm thickness, the frequency is 8.9GHz and the optimum effective wave-absorbing bandwidth (RL) value can reach-71.9 dB.
Claims (9)
1. A preparation method of a core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material is characterized by comprising the following steps of:
step 1: preparation of Ni/Co-MOF precursor:
dissolving sodium salt and nicotinic acid in deionized water and stirring to obtain solution A; putting nickel salt, cobalt salt and polyvinylpyrrolidone into deionized water, and stirring to obtain a solution B; slowly adding the solution B into the solution A and stirring, then transferring the mixed solution into a high-pressure kettle, and reacting for 4-8 hours at the temperature of 100-150 ℃ to obtain a Ni/Co-MOF precursor;
step 2: preparing a Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material:
and pyrolyzing the Ni/Co-MOF precursor for 0.5-2.5 hours at the temperature of 550-700 ℃ in an argon environment at the heating rate of 2-8 ℃/min, and then cooling to obtain the NiCo alloy @ nitrogen-doped carbon-based wave-absorbing composite material Ni/Co @ C with the core-shell structure.
2. The preparation method of the core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material according to claim 1, which is characterized by comprising the following steps of: the mass ratio of the sodium salt to the nicotinic acid to the nickel salt to the cobalt salt is as follows: 1:1:2:1 to 4:5:6: 4.
3. The preparation method of the core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material according to claim 1, characterized by comprising the following steps: the sodium salt is sodium acetate, and the nickel salt is nickel nitrate.
4. The preparation method of the core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material according to claim 1, which is characterized by comprising the following steps of: the cobalt salt is cobalt nitrate.
5. The preparation method of the core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material according to claim 1, which is characterized by comprising the following steps of: preferably, the reaction conditions in step 1 are 120 ℃ for 6 h.
6. The preparation method of the core-shell Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material according to claim 1, which is characterized by comprising the following steps of: in the step 2, preferably, the heating rate is 2 ℃/min, the heat preservation time is 2h, and the calcining temperature is 600 ℃.
7. The use of the core-shell Ni/Co alloy @ nitrogen-doped carbon-based microwave absorbing composite material as claimed in any one of claims 1 to 6 in a microwave absorber.
8. Use according to claim 1, characterized in that: mixing the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material (Ni/Co @ C) with the core-shell structure with paraffin to obtain the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material microwave absorbent.
9. Use according to claim 8, characterized in that: the mass ratio of the Ni/Co alloy @ nitrogen-doped carbon-based wave-absorbing composite material to paraffin is 2: 1-4.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115028847A (en) * | 2022-05-09 | 2022-09-09 | 复旦大学 | CoNi alloy MOF porous material and preparation and application thereof |
| CN115305054A (en) * | 2022-07-08 | 2022-11-08 | 李致朋 | Ternary alloy/porous carbon composite wave-absorbing material and preparation method thereof |
| CN115990493A (en) * | 2022-12-28 | 2023-04-21 | 电子科技大学 | Preparation method of cobalt-based multi-metal sulfide heterostructure nanomaterial |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115028847A (en) * | 2022-05-09 | 2022-09-09 | 复旦大学 | CoNi alloy MOF porous material and preparation and application thereof |
| CN115028847B (en) * | 2022-05-09 | 2024-01-26 | 复旦大学 | CoNi alloy MOF porous material and preparation and application thereof |
| CN115305054A (en) * | 2022-07-08 | 2022-11-08 | 李致朋 | Ternary alloy/porous carbon composite wave-absorbing material and preparation method thereof |
| CN115990493A (en) * | 2022-12-28 | 2023-04-21 | 电子科技大学 | Preparation method of cobalt-based multi-metal sulfide heterostructure nanomaterial |
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